1. Field of the Invention
The present invention relates to air intake filters for combustion engines, compressors, and other air-aspirating machinery and, more particularly, to an air intake filter having a cyclone separator stage arranged upstream of a strainer-type filter element.
2. Description of the Prior Art
The design of an air intake filter of the type under consideration involves a compromise between two opposing requirements: It is desirable, on the one hand, to achieve a high degree of dust separation, in conjunction with an extended service life, in order to avoid the need for frequent servicing of the filter element through cleaning or replacement. On the other hand, the specific machine application in which the air intake filter is used, is frequently subject to limitations of available space and visibility, so that certain overall dimensions cannot be exceeded.
It is known from the prior art that the service life of a filter element with a high degree of dust separation can be considerably increased through the arrangement of a cyclone separator stage upstream of the filter element. The requirement of minimal overall dimensions is being optimally met by arranging the cyclone separation chamber concentrically with the filter element, between the latter and the housing wall of the filter assembly.
A known filter assembly of this type is disclosed in German Gebrauchsmuster (Utility Model) No. 17 11 740. This prior art publication shows, in FIGS. 8 and 9, a fitler assembly with a pot-shaped housing inside which is arranged a hollow-cylindrical filter element of fine-filtering paper surrounded by a cyclone separation chamber. In this chamber, the incoming air is precleaned in an axial cyclone action. The air enters through a series of apertures in the top cover of the assembly, whereupon it is deflected into a helical downward swirl by means of inclined deflector vanes.
Upper and lower cylindrical baffles, with an axial flow gap therebetween, form the inner wall of the cyclone separation chamber. These baffles are spaced a distance from the outer periphery of the filter element so that the precleaned air, after flowing radially inwardly through said gap, is sufficiently distributed over the height of the filter element. One shortcoming of this arrangement is that it requires a considerable radial space for the cyclone stage, reflecting itself in a large overall diameter of the filter assembly. Comparitive tests have shown that, if the radial width of the separation chamber is reduced, because of limited space available, the degree of dust separation is greatly diminished.